The lack of simple, field-friendly point-of-care diagnostic tests remains one of the major challenges in the control of tuberculosis (TB), especially in resource-constrained settings. Host immunological biomarkers have previously been shown as potentially useful diagnostic tools for the disease.

Aim

To validate recently identified host biosignatures and evaluate new candidate biomarkers as tools for the diagnosis of TB in six African countries.

Methods

Serum was collected from individuals presenting with symptoms suggestive of pulmonary TB at seven primary health care clinics situated in six African countries, prior to assessment for TB disease. Using a harmonised diagnostic algorithm comprising laboratory, clinical and radiological findings, participants were later classified as having TB or other respiratory diseases. Biomarkers comprising a previously identified seven-marker serum protein biosignature (CRP, serum amyloid A, IFN-γ, IP-10, complement factor H, apolipoprotein A1 and transthyretin; replaced by Ferritin/NCAM because of technical reasons), and other new biomarkers selected from the literature were evaluated in all study participants using the Luminex multiplex platform.

Results

Of 1004 participants, 278 diagnosed with active TB were included. The previously identified seven-marker biosignature validated on the new cohort with an area under the ROC curve (AUC) of 0.88 (95% CI 0.85-0.91) corresponding to a sensitivity of 90.3% and specificity of 70.2%, respectively, regardless of HIV status or study site. A modified biosignature (CRP, SAP, NCAM, I-309 and GDF-15) diagnosed TB disease in a training sample set (n=677) with an AUC of 0.91 (95% CI 0.88-0.93).

Conclusion

We validated the previously identified seven-marker serum protein biosignature and furthermore, showed that refinement of the biosignature by substitution of some proteins with other biomarkers resulted in an improved diagnosis of active TB, regardless of HIV status or African country sample origin. Our results pave the way for the development of a point-of-care screening test for active TB.